Many pharmaceutical compounds, such as, for example, antiviral, immunosuppressive, and cytotoxic cancer chemotherapy agents, generally have undesirable toxic effects on normal tissues. Such effects, which include damage to bone marrow (with consequent impairment of blood cell production) and gastrointestinal mucosa, alopecia, nausea, etc., limit the dose of a pharmaceutical compound that can be safely administered and thereby reduce the potential efficacy of the pharmaceutical compound.
Targeted drug delivery is an important objective of pharmaceutical research and development. In principle, drug targeting involves directing high concentrations of a pharmacological agent at the pathophysiologically relevant site. If successful, the result of the drug targeting would be a significant reduction in drug toxicity at other sites, thus permitting a reduction of the drug dose, and increased treatment efficacy.
Physical drug targeting approaches have focused on implanting a drug delivery device at or around the target site (for example, organ or tissue). This kind of physical targeting, such as the delivery of pilocarpine to the eye from a polymeric device, has achieved only limited success. Moreover, such a drug delivery methodology is undesirably invasive. Known biological targeting approaches, based on antibodies, in theory, could result in a highly desirable delivery profile. However, there are a number of problems related to the actual distribution of an antibody-drug conjugate in the body that have prevented researchers from achieving any real success. Additionally, biological targeting approaches involving modification of a pharmaceutical compound to have greater affinity for a particular site in a patient's body.
Accordingly, there exists a need for a more effective mechanism of delivering pharmaceutical agents and/or other compounds in vivo that does not suffer from one or more of the problems exhibited by conventional pharmaceutical compound delivery methodologies.